JPS6023431A - Rubber composition having excellent resistance to water containing active chlorine - Google Patents

Abstract

PURPOSE:To provide the titled composition having excellent resistance to water containing active chlorine, e.g. suppressed carbon deposition, etc., and suitable as a rubber product for water supply, by adding carbon black having a pH lower than a specific level to a rubbery polymer. CONSTITUTION:100pts.wt. of a rubbery polymer (e.g. ethylene-propyleneter polymer) is compounded with preferably 5-100pts.wt. of carbon black of <=7pH to obtain the objective composition. The carbon black having a pH of <=7 is preferably channel black or a coloring carbon black, etc. prepared by the surface treatment of furnace black.

Description

DETAILED DESCRIPTION OF THE INVENTION (Purpose and Background) The present invention has excellent resistance to water containing active chlorine, that is, water containing disinfectant chemicals such as chlorine, hypochlorous acid, or hypochlorous acid sorter. - One purpose is to provide a rubber composition.

Conventional rubber products for water supply are natural rubber, S B RlBR
General-purpose rubbers such as those containing carbon black as a reinforcing agent are used. Carbon black is broadly classified into furnace black, channel black, and thermal black depending on its manufacturing method.Channel black has large hysteresis and is acidic with a pH of 4 to 6, which delays vulcanization. Furnace black is mainly used. Furthermore, thermal black has relatively large particles and is used more as a filler than as a reinforcing agent.

When these types of rubber products (hoses, rubber backings for water supplies, flexible expansion joints for water pipes, etc.) are used for a long period of time, carbon black deposits can be seen on their inner surfaces. For example, it is known from experience that when replacing the banking piece of a water faucet after long-term use, your hands get dirty.

However, in recent years, solar water heaters have become widely used as part of energy-saving measures, and rubber products such as rubber hoses are used at higher temperatures than when using tap water, resulting in the carbon precipitation described above. This phenomenon is being further accelerated and causing problems.

For example, if a rubber hose is used to connect the solar heat collector and the hot water storage tank, black foreign matter may be discharged together with the hot water several years after installation, floating in the bathtub, or adhering to the inner wall. This may cause a phenomenon that causes a complaint. It was confirmed that this black foreign material came from the inner surface of the rubber hose and was mainly composed of carbon.

The present inventors investigated this phenomenon and found that the phenomenon of carbon precipitation in rubber products is caused by water containing active chlorine, i.e., chlorine monohypochlorous acid or bactericidal chemicals such as hypochlorous acid Sorg. It was discovered that this phenomenon is particularly noticeable in the case of water containing

(Structure) That is, the present invention is a comb composition containing carbon black having a pH of 7 or less in a rubbery polymer and having excellent resistance to active chlorine-containing water.

The rubbery polymers used as NON materials include natural rubber, polybutanecom (BR), polyisoprene rubber (■R), snalene-butadiene rubber (SBR), butyl rubber, halogenated butyl rubber, chloroprene rubber (CR), acrylic rubber, Silicone rubber, silicone diethylene-propylene rubber, Bar (Paron (trade name: chlorosulfonated polyethylene, DuPont, USA), ethylene-vinyl acetate copolymer (EVA), butadiene-acrylonitrile rubber (NB)
R), 1i hydrogenated polyethylene (CPE), ethylene-propylene rubber (EPM), ethylene-propylene terpolymer (EPDM), etc., and the present invention can be applied effectively to any of them. Among the above, in terms of resistance to active chlorine and other comprehensive characteristics,
EPDM, EPM, solution polymerization SBR, CPE, EVA,
Hypalon, silicone rubber, silicone-ethylene-propylene rubber, acrylic rubber are preferred, and EPDM
, EPM or solution polymerized SBR are preferred. In particular, EPDM with an iodine number of 15 or less and a propylene content of 50% by weight or less
, especially an iodine number of 10 or less and a propylene content of 30% by weight
The following EPDMs are preferably used. In the Examples, the effects of the present invention will be demonstrated using EPDM, which is currently widely used for water supply, as an example.

Further, it is necessary to use a carphone blank with a pH of 7g+ or less, and channel black with a pH of 4 to 6 or so-called carbon solank for color, which is surface-treated furnace black to have a pH of 7 or less, is suitable.

If you choose from among the ones currently on the market considering workability etc., EPC (Easy Processing
Channel) or color capo>・Black is optimal・The formulation is 1 t) O weight part to carbon blank 03~1 0 Makobe, i! Preferably 5~
The lOO hair has 4 parts.

Examples 1-5. Comparative Examples 1-2 Go A, , ll+' (poly and -, (1) iodine 1
Song 95. EPDM with a propylene content of 43 Q% (
(Indicated as EPDM-1 in Table 1) (2) Iodine value 5.3. EPDM with a propylene content of 25 tonne (denoted as EPDM-2 in Table 1) (3) Iodine value 6. O, E with a propylene content of 43% by weight
PDM (denoted as EPDM-3 in Table 1) As a carbon blank, (1) EPC (Easy Processing)
I;hannel) pH=4.41 (2) FET (Fast Extrusion
Furnace) pH=8.45 1 (3) F T (Fine Thermal) pH=
8.43 was used. Other ingredients are as shown in Table 1.

As a method for evaluating 1ml active chlorine properties, a test piece was soaked in a sodium hypochlorite aqueous solution (600 ppm active chlorine concentration).
0° C.), and the time required for the carbon to be wiped off from the rubber with hair was measured.

Note that the active chlorine concentration of water) 6 is approximately ippm, and approximately 300 hours under the above test conditions corresponds to 2 years when used in a solar water heater.

- (Effect) As is clear from Examples 1 to 5 shown in Table 1, the rubber composition of the present invention has active chlorine resistance for more than 1000 hours under test conditions, and for more than 6 years under practical conditions. The active chlorine resistance is far superior to that of the rubber composition containing furnace black (Comparative Example 1), which is currently widely used in water supplies, for 300 hours under test conditions, and approximately 2 years under practical conditions. ing.

Applicant: Brideston Tire Co., Ltd. Agent Patent Attorney Shoji Ao Asa

Claims (1)

[Scope of Claims] 1. A rubber composition containing carbon black having a pH of 7 or less in a rubbery polymer and having excellent resistance to active chlorine-containing water. 2. The rubber composition according to claim 1, which contains carbon blank in an amount of 0.3 to 150 parts by weight based on 100 parts by weight of the rubbery polymer.